1. Technical Field
The present invention relates generally to steer-by-wire systems, and more particularly relates to re-configurable control of steer-by-wire systems.
2. Background Information
Vehicle steering control systems, such as electric power steering control systems and steer-by-wire control systems, are electro-mechanical motion control systems with sensors, actuators, and other electrical and mechanical components. Such systems have become increasingly complex in recent years. It is important for such steering control systems to deal with faults in sensors, actuators, power electronics, and mechanical components. The fault tolerant operation and ability to deal with malfunctions is, therefore, a key issue for vehicle steering control systems, especially for full steer-by-wire systems.
For safe operation of the steer-by-wire control system, hardware redundancy for critical components can be used. However, it is limited by weight and package, cost, space, and similar installation environment for the hardware.
It is possible to eliminate or reduce redundant hardware and to enhance safety by using the analytic redundancy and re-configuration for controller structures and/or parameters of the steer-by-wire systems to maintain the system stability, integrity and certain performance requirements when faults occur in the steer-by-wire control systems.
The present invention provides a re-configurable control for a steer-by-wire system. The re-configurable control maintains the steer-by-wire system to be stable and controllable despite faults that occur in the sensors, actuators, and other mechanical or electrical components.
The steer-by-wire control system has an adaptive re-configurable control structure that is implemented in the steer-by-wire system in accordance with the present invention. This allows a steer-by-wire controller to re-configure its structure and/or parameters to satisfy requirements of stability, integrity and certain performance requirements for the steer-by-wire system.
An adaptive re-configurable control unit is provided with fault detection and isolation, fault decision, parameter identification for the steer-by-wire controlled plant, and a re-configurable controller with automatic adjustable structure and/or parameters.
A residual generator generates a series of residual signals based on the output and input signals of the steer-by-wire controlled plant. The residual signals are evaluated in a fault decision unit to determine whether or not the fault occurs. In the event of a failure, a fault decision signal is given to indicate the fault.
A parameter identifier estimates the model parameters of the steer-by-wire controlled plant in real time. Based on the result of the fault decision signal and the parameter identification, the re-configurable controller reconfigures its structure and/or parameters to compensate for the effects of the fault according to the stability and certain performance requirements of the overall steer-by-wire control system.
The present invention also provides a method of re-configurable control of fault tolerant steer-by-wire systems.
The present invention may include one or more of the following advantages and benefits. The re-configurable control of a steer-by-wire system provides enhanced fault tolerance and safety. Because redundant hardware is eliminated or minimized, the implementation of the re-configurable control results in weight reduction of the vehicle. The system is also cost efficient and has improved system performance and product quality compared to conventional steering systems when the re-configurable control of steer-by-wire system is used. Moreover, the system is easily implemented in embedded systems.
The foregoing discussion has been provided only by way of introduction. Nothing in this section should be taken as a limitation on the following claims, which define the scope of the invention.